How does PSK work?
The generation of a PSK31 signal can best be described in the following sequence of four steps. Actual implementations may not follow precisely this sequence, but the result is the same. 1. Each individual keyboard character is encoded into a string of bits. This is done using a lookup table that implements what Peter Martinez called a Varicode, which is a variable-length encoding scheme. Martinez examined the English language and the frequency of appearance of all the characters, and used shorter bit sequences for the most common characters and longer ones for the less-common ones. (Note this is exactly what Samuel F. B. Morse did approximately 160 years earlier to develop the code that now bears his name.) Unlike RTTY (and Morse), Martinez included both upper-case and lower-case letters, and the lower-case ones get shorter codes because they are more common in written text. He also defined the possibility of extensions to the Varicode to cover additional character sets, for non-Engli
